Evaluation of Hip Muscles using Torque and Power- Velocity Relationships in Chronic Low Back Pain Subjects

The aim of the present study was to evaluate hip muscles in chronic low back pain (CLBP) patients, thanks to the torque- and power-velocity relationships and to determine whether a possible imbalance can be related to the trunk muscles. Twelve CLBP patients and fifteen healthy subjects (Control Group, CG) participated to the study. CLBP and CG performed isokinetic trunk and hip flexions and extensions at several velocities. Mechanical parameters, such as theoretical maximal isometric torque (T0) and maximal power (Pmax) were extrapolated from torque- and power-velocity relationships. T0 and Pmax, were significantly higher in CG than CLBP (p<0.05), whatever the considered movement, showing a muscle weakness in CLBP. A significant difference was obtained between the two lower limbs for CLBP when considering Pmax during hip extension. Although no relationship was clearly observed between hip weakness and trunk weakness for CLBP, results obtained for CLBP could be attributed to a deconditioning syndrome and to muscle inhibition typically observed in these subjects. This study shows the importance to take hip muscle rehabilitation into account in CLBP support.